Five years ago, the weekend that the first Spider-Man movie came out, the American comics industry launched an experiment: Free Comic Book Day, in which thousands of comic book specialty stores around the country gave away comics to readers young and old. It worked out well enough that it’s become an annual tradition, and this Saturday, May 5, is the sixth Free Comic Book Day. Almost every major comics publisher in the country has at least one free title this year, as well as plenty of smaller publishers; the mainstream and indie presses don’t always see eye-to-eye, but they’ve all found that giving away samples is good for business.